System and device for engulfing thrombi

ABSTRACT

A stent retriever for removing a thrombus from a blood vessel includes a body portion formed by a mesh sheet formed into a substantially cylindrical shape. The mesh sheet includes a pair of undulating wire members coupled to a connecting member, each wire member having a plurality of protrusions and a plurality of recesses. The plurality of protrusions on a first side of the mesh sheet are offset from the plurality of protrusions on a second side of the mesh sheet such that when the mesh sheet is formed into the substantially cylindrical shape, the wire members are disposed in an interlocking arrangement such that the recesses on the first side receive at least portions of the protrusions on the second side. At least one of the plurality of protrusions includes a subprotrusion formed in the wire member to increase the mesh density of the stent retriever.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/802,235 filed Nov. 2, 2017 which claims the benefit of and priorityto U.S. Application No. 62/422,870 filed on Nov. 16, 2016. Each of theabove-mentioned applications is hereby incorporated herein by referencein its entirety.

BACKGROUND

Blood flow through the circulatory system can be restricted when athrombus (blood clot) or foreign body develops inside a blood vessel orocclusive thromboembolism occurs. A thrombus is generally formed fromplatelets and fibrin to prevent loss of blood due to an injury to theblood vessel. Serious complications can occur if a thrombus grows toolarge and obstructs too much of the blood vessel. The thrombus may alsobreak loose, forming an embolus that can lodge in another part of thebody, obstructing blood flow and potentially causing irreversible harmto organs or death.

Ischemia is a reduction in blood flow to an organ or tissue, causingdamage due to a lack of sufficient oxygen or fuel being delivered to thecells. One type of stroke (an ischemic stroke) occurs when a cerebralvessel is obstructed (such as by a thrombus or an embolus), reducingblood flow to a specific region of the brain. A blockage of this typecan quickly lead to irreversible damage to brain tissue and death. Itcan be seen, therefore, that there is a great need for effectivetreatment options to remove blood clots to increase the blood flow toorgans such as the brain while minimizing the fragmentation of thethrombus during removal.

A device known as a stent retriever may be utilized to capture andremove a thrombus from a blood vessel. The stent retriever is introducedinto the blood vessel with a catheter. The stent retriever is theinserted into the thrombus and deployed. Upon deployment, the stentretriever expands to engage and capture the thrombus. The stent, alongwith the thrombus, is removed from the vessel, allowing blood to beginflowing again through the vessel. The stent retriever is engulfed in toa large bore catheter so that the thrombus captured and removed by thestent retriever en bloc without fragmentation.

SUMMARY OF THE INVENTION

One embodiment of the invention relates to a system for removing athrombus from a blood vessel. The system includes a stent retriever; afirst catheter, a sheath, and a wire coupled to the stent retriever. Thefirst catheter is configured to receive the stent retriever in acollapsed configuration. The first catheter includes a tubular body anddefining a distal opening and a proximal opening. The wire extendsthrough the proximal opening and the distal opening of the sheath. Thestent retriever is moveable relative to the sheath. The distal openingis sized to allow the stent retriever to be withdrawn into the sheathwithout substantially compressing the stent retriever and the proximalopening is sized to prevent the passage of the removed stent retriever.

Another embodiment of the invention relates to a system for removing athrombus from a blood vessel. The system includes a stent retriever; afirst catheter, and a guide catheter configured to receive the catheter.The first catheter is configured to receive the stent retriever in acollapsed configuration. The guide catheter includes an expandabledistal portion. The diameter of the expandable distal portion is able tovary between a minimum diameter in which the expandable distal portioncomprises a generally cylindrical shape and a maximum diameter in whichthe expandable distal portion comprises a generally non-cylindricalshape in order to occlude the downstream flow to prevent escape of theclot or foreign body from the retrieval device. The stent retriever ismoveable relative to the guide catheter. When the distal portion isexpanded to the maximum diameter, the distal portion defines an openingthat is sized to allow the stent retriever to be withdrawn into thesheath without substantially compressing the stent retriever.

Yet another embodiment of the invention relates to a stent retriever forremoving a thrombus from a blood vessel. The stent retriever includes aplurality of raised portions, and a plurality of lateral recessesdefined between the raised portions. The stent retriever is expandablefrom a compressed configuration to an expanded configuration. Theplurality of lateral recesses receive portions of the thrombus when thestent retriever is in the expanded configuration. The stent retriever isstructured to capture and remove the thrombus or foreign body in onepiece without fragmentation.

The invention is capable of other embodiments and of being practiced orbeing carried out in various ways. Alternative exemplary embodimentsrelate to other features and combinations of features as may begenerally recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become apparent from the following description, appendedclaims, and the accompanying exemplary embodiments shown in thedrawings, which are briefly described below.

FIG. 1A depicts a catheter device introduced into a patient's vascularsystem.

FIG. 1B is an enlarged view of the catheter device of FIG. 1A introducedinto a patient's cerebral vascular system.

FIG. 2 is a side view of a catheter device, according to an exemplaryembodiment.

FIG. 3A is a perspective view of a stent retriever, according to anexemplary embodiment.

FIG. 3B is a side view of a stent retriever according to an exemplaryembodiment, shown opened from a cylindrical form.

FIG. 3C is a side view of a stent retriever according to an exemplaryembodiment, shown opened from a cylindrical form.

FIG. 3D is a cross-section view of the stent retriever of FIG. 3C in acylindrical form.

FIGS. 4A-4D depict the catheter device of FIG. 2 being used to remove athrombus, according to an exemplary embodiment.

FIGS. 5A-5C depict a catheter device including a catheter with a dynamicdistal portion being used to remove a thrombus, according to anexemplary embodiment.

FIG. 6 is a side view of a catheter device, according to anotherexemplary embodiment.

FIGS. 7A-7C depict the catheter device of FIG. 6 being used to remove athrombus, according to an exemplary embodiment.

FIG. 8 is a perspective view of a portion of a catheter device,according to another exemplary embodiment.

FIG. 9 is a perspective view of a portion of a catheter device,according to another exemplary embodiment.

FIGS. 10A-10C depict the catheter device of FIG. 8 or FIG. 9 being usedto remove a thrombus, according to an exemplary embodiment.

FIG. 11 is a perspective view of a stent retriever, according to anotherexemplary embodiment.

FIG. 12 is a perspective view of a stent retriever, according to anotherexemplary embodiment.

FIG. 13 is a perspective view of a stent retriever, according to anotherexemplary embodiment.

FIG. 14 is a perspective view of a stent retriever, according to anotherexemplary embodiment.

FIG. 15 is a cross-section view schematic illustration of the stentretriever of FIG. 14, taken along line 15-15.

FIG. 16 is a side view of a stent retriever according to an exemplaryembodiment, shown opened from a cylindrical form.

FIG. 17 is a perspective view of a stent retriever according to one ormore exemplary embodiments.

FIG. 18 is a perspective view of a stent retriever according to one ormore exemplary embodiments.

DETAILED DESCRIPTION

Catheter systems and methods are used to remove a thrombus from a bloodvessel, such as a cerebral artery, according to several exemplaryembodiments. The catheter system and methods use a stent device which isdeployed to capture the thrombus such that the thrombus is removed fromthe blood vessel with the removal of the stent device. In someembodiments, the stent device and the thrombus are surrounded by asheath or other body to reduce fragmentation of the thrombus and theformation of emboli.

Referring to FIGS. 1A-1B, the catheter device 10 is shown beingintroduced into a patient's vascular system. The catheter device 10includes a base 12 and a delivery or guide catheter 14 that isintroduced into the body. The base 12 (e.g., manifold) includes arotating hemostatic valve (RHV) 16 through which the guide catheter 14extends and allows medical personnel to manipulate the guide catheter14. The guide catheter 14 provides a conduit through which variousinstruments may be deployed to a desired location within the patient'sbody, as described in more detail below.

For a thrombus 30 located in the brain, the catheter device 10 isinserted into the femoral artery 20 through an incision in the thigh.The guide catheter 14 is generally advanced through the femoral artery20 to the aorta 22, through the aorta 22 to a common carotid artery 24(e.g., the left or right common carotid artery). According to theillustrated scenario, the thrombus 30 is located in the middle cerebralartery 28. The guide catheter is therefore advanced through the commoncarotid artery 24 to the internal carotid artery 26. While a thrombuscommonly forms in the middle cerebral artery 28, it will be appreciatedthat the catheter device 10 may be utilized to remove a thrombus locatedelsewhere, such as at the terminus 27 of the internal carotid artery, inthe anterior cerebral artery 29, or in another area of the patient'svascular system.

Referring now to FIG. 2, the catheter device 10 is shown in more detail.The catheter device 10 includes a stent retriever 32. The stentretriever 32 is advanced to the location of the thrombus 30 in acontracted configuration within a microcatheter 34 via a push wire 36.According to an exemplary embodiment, the push wire 36 has a diameter ofapproximately 0.14 inch. In other embodiments, a larger or smallerdiameter push wire may be used. Upon deployment, the stent retriever 32expands, compressing the thrombus against the walls of the blood vesseland captures the thrombus 30. The stent retriever 32 is then retracted,removing the thrombus 30 in the process.

Referring to FIGS. 3A and 3B, the stent retriever 32 is shown in moredetail. FIG. 3A is an illustration of a side view of the stent retriever32 and FIG. 3B is an illustration of an opened, substantially flatconfiguration of the stent retriever 32. The substantially cylindricalstent retriever 32 of FIG. 3A is formed by bringing together the twoside edges of the opened mesh sheet shown in FIG. 3B. According to anexemplary embodiment, the stent retriever 32 is formed from a suitablebiocompatible metal or alloy (e.g., platinum, stainless steel,nickel-titanium alloy, etc.) or a suitable biocompatible polymer. Thestent retriever 32 may be self-expandable or may be expanded withanother device, such as an inflatable balloon. All or part of the stentretriever 32 may be coated or covered with a radiopaque material, suchas platinum to allow for visualization of the stent retriever 32.According to one exemplary embodiment, the stent retriever 32 includesradiopaque markers 33 at a proximal 40 end and a distal end 42 to aid inthe positioning of the stent retriever 32 relative to the thrombus 30.

The stent retriever 32 is an open, generally cylindrical body thatincludes a multitude of protrusions 38 (e.g., fingers, projections,arms, etc.). According to one exemplary embodiment, a row of firstprotrusions 38 a are formed from a first undulating wire member 37 a.The protrusions 38 a are formed as U-shaped members that are orientedlaterally (e.g., generally perpendicular to a longitudinal axis 31 ofthe stent retriever 32). Recesses 39 a (e.g., hollows, depressions,etc.) are formed between each of the protrusions 38 a. The recesses 39 aare U-shaped similar to the protrusions 38 a. A row of secondprotrusions 38 b are formed from a second undulating wire member 37 b.The protrusions 38 b are formed as U-shaped members that are orientedlaterally (e.g., generally perpendicular to the longitudinal axis 31 ofthe stent retriever 32). Recesses 39 b (e.g., hollows, depressions,etc.) are formed between each of the protrusions 38 b. The recesses 39 bare U-shaped similar to the protrusions 38 b. The protrusions 38 a and38 b are disposed in an interlocking (e.g., interdigitated) arrangementsuch that the protrusions 38 a are received in the recesses 39 b and theprotrusions 38 b are received in the recesses 39 a to form thecylindrical stent retriever, as shown in FIG. 3A. This interdigitatedarrangement provides an efficient grab of the thrombus, so that thethrombus can be captured as one piece. The interdigitated arrangementfurther prevents fragmentation of the thrombus while the thrombus arecaptured by the stent retriever 32 and moving along with the stentretriever 32.

In some embodiments, as shown in FIGS. 3C-3D, the protrusions 38 maycomprise a radius of curvature or be otherwise bent at an angle. FIG. 3Cis an illustration of an opened, substantially flattened configurationof the stent retriever 32 but for the curved protrusions, such that thesheet forming the cylindrical stent is not entirely planar. FIG. 3Ddepicts an end view of the stent retriever formed by the sheet of FIG.3C. In this embodiment, protrusions 38 a and 38 b are curved such thatwhen the cylindrical body is formed, the protrusions extend into thebore of the cylinder, as shown in the end view of FIG. 3D. Therefore,when the stent retriever 32 is advanced into the thrombus 30 andexpanded, the protrusions 38 b anchor the thrombus 30 to the stentretriever 32. In the embodiment shown in FIG. 3C, protrusions 38 a arecurved in more drastically than protrusions 38 b. In some embodiments,the protrusions extend at an angle relative to the plane of theconnecting members 35 (described below). In some embodiments, theprotrusions 38 may all comprise the same curvature or inward angle. Inyet further embodiments, the protrusions 38 may have varying degrees ofcurvature or angle along the length of the stent retriever 32. In someembodiments, all of the protrusions 38 are curved or angled in some way.In other embodiments, at least one, but not all, of the protrusions 38comprise a curve or extend at an angle.

The wire members 37 a and 37 b are coupled to each other with connectingmembers 35. According to an exemplary embodiment, the connecting members35 are undulating (e.g., sinusoidal) wire members that are coupled tothe portions of the wire members 37 a and 37 b forming the recesses 39 aand 39 b. In other embodiments, the connecting members may be otherwiseconfigured. For example, in another embodiment, the wire members 37 aand 37 b may be coupled to each other with a multitude of linearconnecting members that extend laterally around the outer circumferenceof the stent retriever 30 between the wire members 37 a and 37 b. Insome embodiments, the connecting members 35 are fixed to the wiremembers 37 a and 37 b. In some embodiments, the connecting members 35and the wire members 37 a and 37 b may be interwoven (e.g., twistedtogether) such that the wire members slide relative to each other as thestent retriever 32 expands or compresses in diameter. The distal end 42of the stent retriever 32 may include a tip 41. In one embodiment, thetip 41 is a 3 mm platinum wire. In some embodiments, the distal end 42of the stent retriever may include additional wire members (e.g., a meshcap) to locally increase the mesh density of the stent retriever 32 andreduce the likelihood that a portion of the thrombus 30 will escape thestent retriever 32 as it is withdrawn.

The protrusions 38 and the recesses 39 facilitate the capturing of thethrombus 30 by the stent retriever 32 and minimize the likelihood ofincomplete capturing of the thrombus that could result in fragmentationand the formation of secondary strokes resulting from of embolisms.According to an exemplary embodiment, the stent retriever has a maximumdiameter of between 1.5 mm and 10 mm when fully expanded. According toan exemplary embodiment, the stent retriever 32 has a length of between10-60 mm. According to some embodiments, the length of the stentretriever 32 is customized according to the size of the thrombus.According to an exemplary embodiment, the stent retriever 32 includesmultiple protrusions 38. The opening of each of the fully expandedU-shaped protrusions may have a size from 1 mm to 3 mm. According to anexemplary embodiment, the diameter of the stent retriever 32 and thesize of the protrusions 38 remain generally constant along the length ofthe stent retriever 32. In other embodiments, as described in moredetail below with regards to FIGS. 11-15, the geometry of the stentretriever may vary along the length of the stent retriever.

It should be noted that the physical dimensions and configurations ofthe stent retriever 32 described above are exemplary only. In otherembodiments, the length, diameter, profile, mesh density, or otherphysical parameter of the stent retriever 32 may be varied based on thelocation and characteristics of the thrombus 30 to be removed.

Referring now to FIGS. 4A-4D, the catheter device 10 including the stentretriever 32 is shown being used to remove the thrombus 30, according toan exemplary embodiment. As shown in FIG. 4A, the guide catheter 14 isadvanced through the patient's vascular system to a position below(e.g., upstream) from the thrombus 30. The guide catheter 14 may beadvanced along a guidewire. According to an exemplary embodiment, theguide catheter 14 is advanced along a 0.35″ diameter guidewire to thedesired location. A microwire 44 is advanced to the thrombus 30 andpierces the thrombus 30 such that a distal end 45 of the microwire 44 isadvanced beyond the thrombus 30. According to an exemplary embodiment,the microwire 44 has a diameter of 0.14″, however, in other embodiments,a larger or smaller diameter microwire may be used.

Referring to FIG. 4B, the micro-catheter 34 is advanced along themicro-wire 44 to pass though the thrombus 30. According to an exemplaryembodiment, the micro-catheter 34 has an inside diameter of between 0.12mm and 0.32 mm, however, in other embodiments, a larger or smallerdiameter micro-catheter may be used to accommodate the diameter of themicrowire 44 and the stent retriever 32. With the micro-catheter 34 inplace, the micro-wire 44 is retracted and the stent retriever 32, in acollapsed configuration, is fed through the micro-catheter 34 via thepush wire 36 until it passes through the thrombus 30 to a point distalto the thrombus 30. In some embodiments, the stent retriever 32 ispositioned with the aid of the radiopaque markers 33.

Referring to FIG. 4C, the stent retriever 32 is held stationary byfixing the push wire 36 at the base 12 of the catheter device 10. Themicrocatheter 34 is retracted to unsheathe the stent retriever 32. Thestent retriever 32 expands to envelop the thrombus 30. According to anexemplary embodiment, the stent retriever 32 is a self-expanding body,however, according to other embodiments, the stent retriever 32 may beotherwise expanded. For example, the stent retriever may be expandedwith a balloon catheter or similar device.

Referring to FIG. 4D, the push wire 36 is released and the stentretriever 32 is withdrawn, removing the thrombus 30 in the process. Inone embodiment, the stent retriever 32 and the removed thrombus 30 areretracted back into the guide catheter 14, which is then withdrawn backthrough the carotid artery 24, the aorta 22, and the femoral artery 20.

Referring now to FIGS. 5A-5C, in one embodiment, the guide catheter 14of the catheter device 10 is a dynamic, expandable body having a distalportion 50 that can be expanded and contracted to vary the outletdiameter 52 of the guide catheter 14. For example, in a defaultconfiguration, as shown in FIG. 5A, the distal portion 50 of the guidecatheter 14 has a first outlet diameter 52 a that is less than the outerdiameter of the stent retriever 32 and a second or expanded diameter 52b that is greater than the outer diameter of the stent retriever 32, asshown in FIG. 5B. At some point between the deployment of the stentretriever 32 at the location of the thrombus 30 and the retraction ofthe stent retriever 32, the position of the guide catheter 14 may beconstrained and the distal portion 50 of the guide catheter 14 may beexpanded to the second outlet diameter 52 b. When expanded to the secondoutlet diameter 52 b, the distal portion 50 of the guide catheter 14forms a funnel-shaped body that facilitates the retraction of the stentretriever 32 and the removed thrombus 30 into the guide catheter 14. Insome embodiments, the second diameter 52 b is equal to the innerdiameter of the blood vessel (e.g., the internal carotid artery 26) inwhich the distal portion 50 of the guide catheter 14 is disposed. Thedistal portion 50 of the guide catheter 14 occludes the blood vessel andtemporarily prevents the flow of blood past the stent retriever 32 asthe thrombus 30 is being retracted towards the guide catheter 14,minimizing the likelihood of fragmentation of the thrombus 30. Thedistal portion 50 of the guide catheter 14 has a sufficient rigidity toresist the fluid force of the blood flow and maintain the funnel-shapedprofile of the distal portion 50 when expanded to the second outletdiameter 52 b. As shown in FIG. 5C, after the stent retriever 32 and theremoved thrombus 30 have been retracted into the guide catheter 14, thedistal portion 50 may be contracted again to a third outlet diameter 52c that is less than the outer diameter of the stent retriever 32. Inthis configuration, the distal portion 50 envelops the stent retriever32 and the removed thrombus 30 as they are removed from the patient. Insome embodiments, the third outlet diameter 52 c is approximately equalto the first outlet diameter 52 a.

The distal portion 50 of the guide catheter 14 may be expanded andcontracted by various means to vary the outlet diameter 52. For example,according to one exemplary embodiment, the distal portion 50 is expandedand contracted by torque mechanisms, string mechanisms, or springmechanisms.

Referring now to FIGS. 6-7C, in some embodiments, the catheter device 10may further include a flexible sheath 60 (e.g., cover, shroud, sleeve,etc.). The sheath 60 is a tubular member that is configured to envelopor engulf the stent retriever 32 and the removed thrombus 30. The sheath60 is formed from a flexible bio-compatible polymer or metal wire mesh.The sheath 60 is formed from a tight mesh to secure the thrombus andprevent fragments of the thrombus 30 from escaping as the thrombus 30 isbeing removed from the blood vessel. The sheath 60 forms a distalopening 62 through which the stent retriever 32 and the thrombus 30 maybe retracted into the sheath 60 and a smaller proximal opening 64. In anexpanded configuration, the distal opening 62 of the sheath 60 is largeenough and the sheath 60 has a length that is large enough to receivethe stent retriever 32 and the removed thrombus 30. In one embodiment,the sheath 60 has a distal opening 62 with a diameter of between 4 mmand 7 mm and a length of between 20 mm and 60 mm. The proximal opening64 is large enough to allow the push wire 36 of the stent retriever 32to pass freely through the sheath 60 without binding but does not allowthe stent retriever 32 to pass through. A mechanism, shown as a stopper66 provided at a point along the length of the push wire 36, limits thetravel of the stent retriever 32 relative to the sheath 60. The stopper66 has a diameter larger than the diameter of the proximal opening 64.

Referring to FIG. 7A, the sheath 60 is advanced through the patient'svascular system in a collapsed configuration within a catheter. Forexample, according to one embodiment, the sheath 60 is collapsed withinthe microcatheter 34 with the stent retriever 32. The microcatheter 34is advanced along a microwire 44 to pass though the thrombus 30, asdescribed above with respect to FIG. 4B. With the microcatheter 34 inplace, the microwire 44 is retracted and the stent retriever 32 and thesheath 60, both in a collapsed configuration, are fed through themicrocatheter 34 until the stent retriever 32 passes through thethrombus 30. The sheath 60 is advanced through the microcatheter 34through the interaction between the stopper 66 and the proximal portion63 of the sheath 60.

Referring to FIG. 7B, the stent retriever 32 is held stationary byfixing the push wire 36 at the base 12 of the catheter device 10. Themicrocatheter 34 is retracted to unsheathe the stent retriever 32 andthe sheath 60. The stent retriever 32 expands to compress the thrombus30 against the walls of the blood vessel. The sheath 60 is disposed inthe patient's blood vessel at some point upstream from the stentretriever 32 and the thrombus 30. The sheath 60 may be provided at anydistance from the thrombus 30, depending on the position of the stopper66. In an exemplary embodiment, the stopper 66 is disposed along thepush wire 36 between 3 cm and 12 cm from the stent retriever 32. In someembodiments, the positioning of the sheath 60 relative to the thrombus30 is determined based on the size and shape of the blood vessel. Thesheath 60 is expanded when outside the microcatheter 34. In someembodiments, the diameter of the distal portion 61 of the sheath 60 isequal to the inner diameter of the blood vessel (e.g., the internalcarotid artery 26) so that the distal portion 61 of the sheath 60occludes the blood vessel and temporarily prevents the flow of bloodpast the stent retriever 32 as the thrombus 30 is being retractedtowards the sheath 60, minimizing the likelihood of fragmentation of thethrombus 30. In other embodiments, the sheath 60 may not occlude theblood vessel and the blood vessel may be otherwise occluded, such as viathe inflation of a balloon upstream from the sheath 60.

Referring to FIG. 7C, the push wire 36 is released and the stentretriever 32 is withdrawn, removing the thrombus 30 in the process. Thesheath 60 remains stationary as the stent retriever 32 and the removedthrombus 30 are retracted. The stent retriever 32 and the removedthrombus 30 are moved into the sheath 60, which is withdrawn from thevascular system along with the stent retriever 32 and the removedthrombus 30. The sheath 60 protects the stent retriever 32 and theremoved thrombus 30 during the withdrawal process.

Referring now to FIGS. 8-10C, in some embodiments, the catheter device10 may include a flexible sheath 70 (e.g., cover, shroud, sleeve, etc.)that may be added to an existing stent retriever system. The sheath 70is similar to sheath 60 and is a tubular member that is configured toenvelop or engulf the stent retriever 32 and the removed thrombus 30.The sheath 70 defines a distal opening 72 and a proximal opening 74. Apush wire 76 is coupled to the proximal portion 74 of the sheath 70.According to an exemplary embodiment, the push wire 76 has a diameter ofbetween 0.07″ and 0.14″. According to another exemplary embodiment, thepush wire 76 has a diameter of between 0.07″ and 0.10″. Themicrocatheter 34 passes through the proximal opening 74 and through thedistal opening 72. In an expanded configuration, the distal opening 72of the sheath 70 is large enough and the sheath 70 has a length that islarge enough to receive the stent retriever 32 and the removed thrombus30, similar to the sheath 60, as shown in FIG. 6. The proximal opening74 is large enough to allow the microcatheter 34 to pass freely throughthe sheath 70 without binding. The sheath 70 and the stent retriever 32,which is compressed within the microcatheter 34, are housed within anouter microcatheter 78. The outer microcatheter 78 defines a distalopening 73, a proximal opening 75 through which the push wire 76 passes,and, in the embodiment of FIG. 8, a side opening 77 through which themicrocatheter 34 passes. The embodiment shown in FIG. 9 is similar tothat of FIG. 8, except that the outer microcatheter 78 does not includea side opening 77 and microcatheter 34 passes through the proximalopening 75 of the outer microcatheter 78.

The sheath 70 may be used with an existing stent retriever system byfirst inserting the sheath 70 into the outer microcatheter 78 throughthe proximal opening 75. The microcatheter associated with the existingstent retriever system may be inserted through the side opening 77, intothe interior of the outer microcatheter 78, through the proximal opening74 and the distal opening 72 of the sheath 70, and through the distalopening 73 of the outer microcatheter 78. In another embodiment, thesheath 70 may be inserted into the outer microcatheter 78 through theside opening 77. The microcatheter associated with the existing stentretriever system may be inserted through the proximal opening 75, intothe interior of the outer microcatheter 78, through the proximal opening74 and the distal opening 72 of the sheath 70, and through the distalopening 73 of the outer microcatheter 78. The outer microcatheter 78 maythen be inserted into the body via the RHV 16 of the base 12 and theguide catheter 14.

Referring to FIG. 10A, the guide catheter is advanced through thepatient's vascular system to a position below (e.g., upstream) from thethrombus 30. The guide catheter 14 is then retracted to expose the outermicrocatheter 78. The outer microcatheter 78 is fixed in place and thesheath is fixed in place via the push wire 76. The microcatheter 34 isadvanced to pass though the thrombus 30 over a microwire. With themicrocatheter 34 in place, the microwire is retracted and the stentretriever 32, in a collapsed configuration, is fed through themicrocatheter 34 until it passes through the thrombus 30 to a pointdistal to the thrombus 30. In some embodiments, the stent retriever 32is positioned with the aid of the radiopaque markers 33.

Referring to FIG. 10B, the stent retriever 32 is held stationary byfixing the push wire 36 at the base 12 of the catheter device 10. Themicrocatheter 34 is retracted to unsheathe the stent retriever 32. Thestent retriever 32 expands to compress the thrombus 30 against the wallsof the blood vessel. The sheath 70 is positioned independently of thestent retriever 32. The sheath 70 and/or the outer microcatheter 78 canbe advanced to any desired location relative to the thrombus 30. Forexample, as illustrated in FIG. 10B, the outer microcatheter 78 may beadvanced to a point in the blood vessel in close proximity to thethrombus 30, minimizing the distance traveled by the stent retriever 32and the removed thrombus 30 before being received by the sheath 70.However, in other embodiments, the outer microcatheter 78 may beadvanced to a point further upstream from the thrombus 30. In someembodiments, the positioning of the outer microcatheter 78 and thesheath 70 relative to the thrombus 30 is determined based on the sizeand shape of the blood vessel.

Referring to FIG. 10C, the sheath 70 is then deployed by fixing the pushwire 76 and retracting the outer microcatheter 78. The sheath 70 isexpanded when outside the outer microcatheter 78, as described abovewith respect to the sheath 60. In some embodiments, the sheath 70 may becompletely deployed from the outer microcatheter 78, as illustrated inFIG. 10C. In other embodiments, the sheath 70 may only be partiallydeployed from the outer microcatheter 78 such that it forms a funnelstructure for receiving the stent retriever 32 and the removed thrombus30 in the outer microcatheter 78. Once the sheath 70 is deployed, thepush wire 36 is released and the stent retriever 32 is withdrawn,removing the thrombus 30 in the process. The sheath 70 remainsstationary as the stent retriever 32 and the removed thrombus 30 areretracted. The stent retriever 32 and the removed thrombus 30 are movedinto the sheath 70, which is withdrawn from the vascular system alongwith the stent retriever 32 and the removed thrombus 30. The sheath 70protects the stent retriever 32 and the removed thrombus 30 during thewithdrawal process. According to some embodiments, the sheath 70 and thestent retriever 32 may be loaded separately over the push wire 76.According to some embodiments, the sheath 70 and the stent retriever 32may be combined as one piece covered retriever. According to someembodiments, the sheath 70 and the stent retriever 32 may be retrievesimultaneously.

While the stent retriever in FIGS. 5A-7C is shown as the stent retriever32, the sheaths 60, 70, or 80 may be configured for use with anyexisting stent retriever designs. For example, the sheaths 60, 70, and80 may be configured for use with the Solitaire™ revascularizationdevice, marketed by Medtronic; the Mindframe device, marketed byMedtronic; the Trevo® device, marketed by Stryker; the Embotraprevascularization device, marketed by Neuravi; or any other similardevices.

Referring now to FIGS. 11-13, the stent retriever 32 is shown accordingto other exemplary embodiments. The stent retriever 32 has a length 90and a diameter 92. The protrusions 38 are shown to have a length 94, anda width 96. Referring back to FIGS. 3A-C in one embodiment, the width 96of the protrusions 38 and the diameter 92 may be constant. As shown inFIG. 3B, the interlocking protrusions 38 may have a length 94 such thatthey comprise approximately ⅓ of the total circumference of the stentretriever. In other embodiments, the length 94 of the protrusions may begreater, such that they comprise a greater portion of the totalcircumference of the stent retriever 32 or may be lesser, such that theycomprise a lesser portion of the total circumference of the stentretriever 32.

In another embodiment, the diameter 92 of the stent retriever 32 and thedensity (e.g., wire density, mesh density, etc.) of the stent retriever32 may vary along the length of the stent retriever 32. The diameter 92of a first portion of the stent retriever 32 may be diameter and thediameter 92 of a second portion of the stent retriever 32 may have adifferent diameter. For example, as shown in FIG. 11, a proximal portion100 of the stent retriever 32 may have a first diameter 92 a and adistal portion 102 of the stent retriever 32 may have a second diameter92 b that is less than the first diameter 96 a. In this way the meshdensity of the distal portion 102 may be greater than the density of theproximal portion 100. In some embodiments, the diameter 92 is decreasedgradually along the length 90, so that at the distal end of the stentretriever 32, the diameter 92 is smaller than the proximal end of thestent retriever 32. In some embodiments, the diameter 92 is increasedgradually along the length 90, so that at the distal end of the stentretriever 32 the diameter 92 is larger than then the proximal end of thestent retriever 32.

In another embodiment, the width 96 of the protrusions 38 and thedensity (e.g., wire density, mesh density, etc.) of the stent retriever32 may vary along the length of the stent retriever 32. The protrusions38 of a first portion of the stent retriever 32 may have a width and theprotrusions 38 of a second portion of the stent retriever 32 may have adifferent width. For example, as shown in FIG. 12, the protrusions 38 ofthe proximal portion 100 of the stent retriever 32 may have a firstwidth 96 a and the protrusions 38 of the distal portion 102 of the stentretriever 32 may have a second width 96 b that is less than the firstwidth 96 a. In this way the mesh density of the distal portion 102 maybe greater than the density of the proximal portion 100.

In another embodiment, both the diameter 92 of the stent retriever 32and width 96 of the protrusions 38 may vary along the length of thestent retriever 32. For example, as shown in FIG. 13, the diameter 92 aof the proximal portion 100 of the stent retriever 32 may be greaterthan the diameter 92 b of the distal portion 102 and the width 96 a ofthe protrusions 38 of the proximal portion 100 may be greater than thewidth 96 b of the protrusions 38 of the distal portion 102.

Referring now to FIGS. 14-15, a stent retriever 132 is shown accordingto another exemplary embodiment with overlapping protrusions 138. FIG.14 depicts a side view of stent retriever 132 and FIG. 15 depicts an endview of stent retriever 132, showing overlapping protrusions 138 a and138 b when the stent sheet is formed into a cylindrical body. Similar tothe stent retriever 32, the stent retriever 132 is formed from asuitable biocompatible metal or alloy (e.g., platinum, stainless steel,nickel-titanium alloy, etc.) or a suitable biocompatible polymer. Thestent retriever 132 may be self-expandable or may be expanded withanother device, such as an inflatable balloon. All or part of the stentretriever 132 may be coated or covered with a radiopaque material, suchas platinum to allow for visualization of the stent retriever 132. Thestent retriever 132 includes a proximal 140 end and a distal end 142.

The stent retriever 132 is an open, generally cylindrical body thatincludes a multitude of protrusions 138 a and 138 b (e.g., fingers,projections, arms, etc.). According to one exemplary embodiment, a rowof first protrusions 138 a are formed from a first undulating wiremember 137 a. The protrusions 138 a are formed as U-shaped members thatare oriented laterally (e.g., generally perpendicular to a longitudinalaxis 131 of the stent retriever 132). A row of second protrusions 138 bare formed from a second undulating wire member 137 b. The protrusions138 b are formed as U-shaped members that are oriented laterally (e.g.,generally perpendicular to the longitudinal axis 131 of the stentretriever 132).

The wire members 137 a and 137 b are coupled to each other withconnecting members 135. According to an exemplary embodiment, theconnecting members 135 are undulating (e.g., sinusoidal) wire membersthat are coupled to the portions of the wire members 137 a and 137 bforming the recesses 139 a and 139 b. In other embodiments, theconnecting members may be otherwise configured. For example, in anotherembodiment, the wire members 137 a and 137 b may be coupled to eachother with a multitude of linear connecting members that extendlaterally around the outer circumference of the stent retriever 30between the wire members 137 a and 137 b. In some embodiments, theconnecting members 135 are fixed to the wire members 137 a and 137 b. Insome embodiments, the connecting members 135 and the wire members 137 aand 137 b may be interwoven (e.g., twisted together) such that the wiremembers slide relative to each other as the stent retriever 132 expandsor compresses in diameter.

The protrusions 138 a and 138 b are disposed in an overlappingarrangement such that the protrusions 138 a overlap (e.g., pass over,pass under, etc.) the protrusions 138 b. The protrusions 138 a areformed with a first radius 150 a and the protrusions 138 b are formedwith a second radius 150 b that is less than the first radius 150 a.According to an exemplary embodiment, the second radius 150 b is between25% and 100% of the first radius 150 a. According to a preferredembodiment, the second radius 150 b is approximately 50% of the firstradius 150 a. By providing the protrusions 138 a and 138 b at differentradii, the protrusions 138 a and 138 b can interact with the thrombus 30in different ways. For example, in one embodiment, the protrusions 138 bhave a radius that is less than the radius of the thrombus 30.Therefore, when the stent retriever 132 is advanced into the thrombus 30and expanded, the protrusions 138 b anchor the thrombus 30 to the stentretriever 132. Meanwhile, the protrusions 138 a surround the thrombus 30and prevent the escape of the thrombus 30 as the stent retriever 132 isretracted.

In some embodiments, the protrusions 138 a and 138 b may be formed withdifferent densities. In one embodiment, the protrusions 138 a are formedwith a relatively dense mesh to reduce the likelihood that any portionof the thrombus escapes as the stent retriever 132 is retracted whilethe protrusions 138 b are formed with a relatively loose mesh to reduceunnecessary fragmentation of the thrombus 30.

Referring now to FIG. 16, an illustration of an opened, substantiallyflat view of a mesh sheet of another stent retriever 232 is shown. Thestent retriever 232 is configured similar to the stent retriever 32described above and includes a first undulating wire member 237 a and asecond wire member 237 b. The wire members 237 a and 237 b are coupledto each other with connecting members 235. The first wire member 237 aforms a row of first protrusions 238 a and recesses 239 a. The secondwire member 237 b forms a row of second protrusions 238 b and recesses239 b. The protrusions 238 a and 238 b are disposed in an interlocking(e.g., interdigitated) arrangement such that the protrusions 238 a arereceived in the recesses 239 b and the protrusions 238 b are received inthe recesses 239 a.

According to an exemplary embodiment, one or more of the protrusions 238a and 238 b are formed to include sub-protrusions 242 a and 242 b,increasing the mesh density of the stent retriever 232. Increasing themesh density of the stent retriever 232 reduces the likelihood that aportion of the thrombus 30 will escape the stent retriever 232. Thesub-protrusions 242 a extend into the U-shaped openings 240, decreasingthe area of the openings 240. The sub-protrusions 242 b extend out fromthe U-shaped openings 240. Sub-protrusions 242 b are configured to bereceived by sub-protrusions 242 a when the stent retrieve 232 is formedinto a cylindrical body. In the embodiment of FIG. 16, thesub-protrusions 242 a and 242 b are formed as U-shaped members. In otherembodiments, the sub-protrusions may be otherwise formed, such as in asaw-tooth pattern. Similar to the embodiment of FIGS. 3C-3D, theprotrusions 238 of stent retriever 232 may also be formed with a curveor at an angle, such that the protrusions extend into the bore of thecylindrical stent retriever body.

Referring now to FIG. 17, a perspective view of a stent retriever 332 isshown according to one or more embodiments. The stent retriever 332includes multiple protrusions 338 a and 338 b. The protrusions 338 a and338 b extend inward from the outer periphery of the stent retriever 332.According to some embodiments, the opening of the protrusions 338 a and338 b are arranged to face different directions, so that the protrusion338 a and protrusion 338 b do not meet at the center of the circle. Forexample, the opening of the protrusion 338 a may face a direction with adesired angle to the direction of the protrusion 338 b. According tosome embodiments, the protrusion 338 a and the protrusion 338 b arearranged to maximize the contact area between the stent retriever 332and thrombus in order to reduce the likelihood that the thrombus willescape as the stent retriever 332 is retracted.

Referring to FIG. 18, a perspective view of a stent retriever 400 isshown according to one or more embodiments. The retriever 400 includesmultiple circular elements 402. According to some embodiments, thenumber of the circular elements 402 of the retrievers 400 may bedetermined according to the size of the thrombus. According to someembodiments, the circular elements 402 may have different sizes. Forexample, the circular element in the middle of the retriever 400 haslarger size than the circular element in a distal end and circularelement in a proximal end of the retriever 400. According to someembodiments, the size of the circular elements 402 may be graduallydecreased from middle portion to the end portions.

The circular element 402 includes a protrusion 404 and protrusion 406.According to some embodiments, the protrusions 404 and 406 are formed asU-shaped members. According to some embodiments, the openings of theprotrusions 404 and 406 are arranged to face different directions toprovide larger contact area between the stent retriever 400 and thrombusin order to reduce the likelihood that the thrombus will escape as theretriever 400 is retracted. For example, if viewing the circular element402 as a clock, the protrusion 404 faces 1 o'clock direction, and theprotrusion 406 faces 7 o'clock direction.

According to some embodiments, the circular elements 402 are connectedwith each other by four straight wires 414, 416, 418, and 420. Accordingto some embodiments, the four straight wires divided the retriever 400into four equal zones. According to some embodiments, within each zone,a zigzag wire 422 is connected to each circular element 402 to hold thecircular element in place. According to some embodiments, at the distaland proximal end of the retriever, multiple straight wires are connectedto one or two circular elements to form a mesh zone in order to captureany fragments of the thrombus.

The retriever 400 further includes three opaque markers 410 at each endof the retriever 400. The opaque markers 410 may be used to aid in thepositioning of the stent retriever 400 relative to the thrombusaccording to some embodiments.

The construction and arrangement of the elements of the catheters forengulfing thrombi as shown in the various exemplary embodiments isillustrative only. Although only a few embodiments have been describedin detail in this disclosure, those skilled in the art who review thisdisclosure will readily appreciate that many modifications are possible(e.g., variations in sizes, dimensions, structures, shapes andproportions of the various elements, values of parameters, mountingarrangements, use of materials, colors, orientations, etc.) withoutmaterially departing from the novel teachings and advantages of thesubject matter recited herein. For example, elements shown as integrallyformed may be constructed of multiple parts or elements, the position ofelements may be reversed or otherwise varied, and the nature or numberof discrete elements or positions may be altered or varied. It should benoted that the elements and/or assemblies of the system may beconstructed from any of a wide variety of materials that providesufficient strength, durability, or biocompatibility. Othersubstitutions, modifications, changes and omissions may be made in thedesign, operating conditions and arrangement of the preferred and otherexemplary embodiments and medical procedures without departing from thescope of the present invention.

What is claimed is:
 1. A stent retriever for removing a thrombus from ablood vessel, the stent retriever comprising: a body portion formed by amesh sheet formed into a substantially cylindrical shape; wherein themesh sheet comprises a pair of undulating wire members coupled to aconnecting member, each of the pair of wire members comprising aplurality of protrusions and a plurality of recesses defined between theplurality of protrusions; wherein the plurality of protrusions on afirst side of the mesh sheet are offset from the plurality ofprotrusions on a second side of the mesh sheet such that when the meshsheet is formed into the substantially cylindrical shape by bringing thefirst and second side of the mesh sheet together, the wire members aredisposed in an interlocking arrangement such that the plurality ofrecesses on the first side of the mesh sheet receive at least portionsof the plurality of protrusions on the second side of the mesh sheet;and wherein at least one of the plurality of protrusions includes atleast one subprotrusion formed in the wire member to increase the meshdensity of the stent retriever.
 2. The stent retriever of claim 1,wherein the plurality of protrusions on the first and second side of themesh sheet are curved upward from the connecting member of the meshsheet such that when the mesh sheet is formed into the substantiallycylindrical shape, the protrusions alternatingly extend into a bore ofthe substantially cylindrical body portion.
 3. The stent retriever ofclaim 2, wherein the at least one subprotrusion is curved upward fromthe mesh sheet in a different plane than the curve of the plurality ofprotrusions such that when the mesh sheet is formed into thesubstantially cylindrical shape, the at least one subprotrusion extendsinto a bore of the substantially cylindrical body portion
 4. The stentretriever of claim 1, wherein at least one of the plurality ofprotrusions on the first side comprises at least one subprotrusionextending into the area of the protrusion.
 5. The stent retriever ofclaim 1, wherein at least one of the plurality of protrusions on thesecond side comprises at least one subprotrusion extending outside ofthe area of the protrusion.
 6. The stent retriever of claim 1, wherein:at least one of the plurality of protrusions on the first side comprisesat least one subprotrusion extending into the area of the protrusion; atleast one of the plurality of protrusions on the second side comprisesat least one subprotrusion extending outside of the area of theprotrusion; and the at least one subprotrusion extending into the areaof the protrusion on the first side is configured to receive a portionof the at least one subprotrusion extending outside of the area of theprotrusion on the second side, when the first side and the second sideof the mesh sheet are brought together to form the substantiallycylindrical shape.
 7. The stent retriever of claim 1, wherein each ofthe plurality of protrusions comprises at least one subprotrusion. 8.The stent retriever of claim 1, wherein the at least one subprotrusionis u-shaped.
 9. The stent retriever of claim 1, wherein the at least onesubprotrusion comprises a saw-tooth shape.
 10. The stent retriever ofclaim 1, wherein the stent retriever comprises a length of between 10 mmand 60 mm.
 11. A system for removing a thrombus from a blood vessel, thecatheter device comprising: a stent retriever; and a guide catheterconfigured to receive the stent retriever, the guide catheter comprisingan expandable distal portion; wherein the stent retriever is moveablerelative to the guide catheter; and wherein the expandable distalportion comprises an outlet, and wherein a diameter of the outlet isvariable between a first diameter that is less than an outer diameter ofthe stent retriever, a second diameter that is greater than the outerdiameter of the stent retriever for receiving the stent retrieverthrough the outlet, and once the stent retriever has been moved throughthe outlet, a third diameter that is less than an outer diameter of thestent retriever to envelope the stent retriever in the guide catheter.12. The system of claim 11, wherein when the outlet is expanded to thesecond diameter, the outlet is sized to allow the stent retriever to bewithdrawn into the guide catheter without substantially compressing thestent retriever.
 13. The system of claim 11, wherein the third diameteris substantially equal to the first diameter.
 14. The system of claim11, further comprising one or more mechanisms to expand and contract theexpandable distal portion.
 15. The system of claim 14, wherein the oneor more mechanisms comprise at least one of a torque mechanism, a stringmechanism, a spring mechanism, or a combination thereof.
 16. The systemof claim 11, wherein a body of the expandable distal portion isexpandable between a minimum diameter and a maximum diameter.
 17. Thesystem of claim 16, wherein the maximum diameter allows the stentretriever to be withdrawn into the guide catheter without substantiallycompressing the stent retriever
 18. The system of claim 16, wherein theexpandable distal portion, when expanded to the maximum diameter,occludes a blood vessel in which it is disposed.
 19. The system of claim18, wherein the second diameter of the outlet is substantially equal tothe maximum diameter of the expandable distal portion.
 20. The system ofclaim 11, wherein the stent retriever comprises: a body portion formedby a mesh sheet formed into a substantially cylindrical shape; whereinthe mesh sheet comprises a pair of undulating wire members coupled to aconnecting member, each of the pair of wire members comprising aplurality of protrusions and a plurality of recesses defined between theplurality of protrusions; wherein the plurality of protrusions on afirst side of the mesh sheet are offset from the plurality ofprotrusions on a second side of the mesh sheet such that when the meshsheet is formed into the substantially cylindrical shape by bringing thefirst and second side of the mesh sheet together, the wire members aredisposed in an interlocking arrangement such that the plurality ofrecesses on the first side of the mesh sheet receive at least portionsof the plurality of protrusions on the second side of the mesh sheet;and wherein at least one of the plurality of protrusions includes atleast one subprotrusion formed in the wire member to increase the meshdensity of the stent retriever.